Here is another smart treadmill with speakers and Bluetooth that gives you a good workout indoors. The Sunny Health & Fitness SF-T7515 Smart Treadmill has 12 levels of incline from 0 to 12%. It has 3 countdown modes and speed range from 1 to 8 miles per hour. It comes with a pulse grip heart monitor and an integrated BMI calculator.
This treadmill has an easy folding mechanism for storage. It also has wheels for transportation. The SF-T7515 has a running surface of 49.5L x 16.5W. You can find out more about it here.